Electronic – loop area and EMI

emcgroundloopsRF

I always hear something like "reduce the loop area" when reading materials on EMI reduction. Why we need to minimize the loop area? I have two guesses:

  1. Smaller loop area will influence less signal tracks, since it will overlap with less tracks.
  2. Small loop area will radiate less?? (If so, why is this?)

Are my guesses correct? How could I learn the EMI issue with in a more systematic way, maybe starting on teaching myself RF theories?

Best Answer

At a high level ... I hope someone else will explain in more detail and with the underlying theory.

Loops have to do with magnetic coupling / interference / compatibility between two circuits.

With a larger loop, more magnetic field lines will fit inside the loop, so the magnetic coupling between this loop on your PCB and an interfering outside magnetic field can be better. If you make your loop infinitely small, then no field lines fit inside your loop, hence no magnetic coupling is possible.

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